1. Field of the Invention
The present invention relates to a rotary encoder operated by rotary manipulation of an outer periphery thereof.
2. Background Art
In any of portable terminals, IT-related apparatuses and vehicle-mounted control apparatuses, there is a tendency in recent years that an operating panel has a single device for centralized manipulation, and a demand thus exists in the market for a prolonged service life of such operating devices.
Referring to FIG. 15 through FIG. 17, description is provided of a rotary encoder (hereinafter referred to as “encoder”) as an example of such conventional operating devices.
FIG. 15 is a sectional view of a conventional encoder. FIG. 16 is an exterior view of the encoder shown in FIG. 15. FIG. 17 is an exploded perspective view of the encoder shown in FIG. 15.
In FIG. 15 through FIG. 17, substrate 1 made of an insulating resin is provided with a pair of confronting supports 2 (hereinafter referred to as “supports 2”) at a fringe of it. Quadrangular frame 3 is pivotally supported by supports 2 to substrate 1. Rotary body 4 is retained in a rotatable manner to frame 3. Rotary body 4 has large cylindrical shaped knob 5 at its center portion. Knob 5 has a hollow and is made of a resin. And, rotary body 4 has cylindrical shafts 6A and 6B (hereinafter “shafts 6A and 6B”) of a small diameter at both ends of it. Shaft 6A is provided with movable contact 7 (hereinafter referred to as “contact 7”) on its outer periphery, and shaft 6B is provided with undulated surface 8 also on its outer periphery. In other words, cylindrical shaft 6 (hereinafter referred to as “shaft 6”) of the small diameter provided with contact 7 and undulated surface 8 near the both ends of it is inserted in and fixed to center hole 5A of knob 5, to constitute rotary body 4. Contact 7 has cylindrical contact portion 7A (hereinafter referred to as “contact portion 7A”) and comb-tooth contact portion 7B (hereinafter referred to as “contact portion 7B”).
Three flexible stationary contacts 9A, 9B and 9C (hereinafter referred to as “contacts 9A, 9B and 9C”) secured to substrate 1 are in contact resiliently with contact 7. Plate spring 10 extended from substrate 1 is also in resilient contact with undulated surface 8.
In addition, self-resettable type push switch 11 is disposed to substrate 1 in a manner to be operated when depressed by a turning movement of frame 3. Cover 12 is then placed to enclose both ends of rotary body 4, to complete the rotary encoder.
Frame 3 has four sides 14A, 14B, 15A and 15B. Side 14A is provided with pivot shafts 13 (hereinafter referred to as “pivots 13”). Sides 14A and 14B are arranged opposite to each other. Two opposite sides 15A and 15B are in continuity to sides 14A and 14B respectively at right angles.
Pivots 13 are inserted in support holes 2A formed in supports 2, frame 3 is pivotally supported to substrate 1. In addition, projections 16A and 16B formed at both ends of side 14B are inserted in restraining holes 17A and 17B to limit a range of pivoting angle of frame 3. Restraining holes 17A and 17B are provided on substrate 1 at a side opposite supports 2.
U-shaped retaining slots 18A and 18B, each having a narrowly cutout opening at the upper side, are formed in generally the center of respective sides 15A and 15B. Shafts 6A and 6B are pressed from the upper side to fit into retaining slots 18A and 18B to ratably hold shaft 6.
In the structure described above, shaft 6 rotates and the rotary encoder operates when a force is applied to knob 5 in a direction tangent to its outer periphery.
That is, as rotary body 4 rotates, contacts 9A, 9B and 9C slide on contact portions 7A and 7B while maintaining resilient contact with them. This produces electrical signals between connection terminals 9D and 9E, and between connection terminals 9D and 9F as these terminals 9D, 9E and 9F are electrically in continuity to contacts 9A, 9B and 9C respectively.
At the same time, detent 10A formed on flexible plate spring 10 slides over undulated surface 8 while maintaining resilient contact to it. This produces tactile responses corresponding to the electrical signals. Detent 10A is then caught in one of slits in undulated surface 8 when rotary body 4 stops rotation.
When a depressing force is applied downward to knob 5, frame 3 turns at pivots 13. This causes depressing boss 14C formed on the underside at side 14B to depress and actuate push switch 11.
The above example of the prior art is disclosed in Japanese Patent Unexamined Publication, No. 2001-084877, for instance.
In the conventional rotary encoder, however, contacts 9A, 9B and 9C slide on contact portions 7A and 7B while maintaining resilient contact at all the time. As a result, contacts 9A, 9B and 9C and contact portions 7A and 7B wear out at their contacting points due to the rotating operations, which makes it difficult to prolong the service life.